The present invention relates to a resist material of positive type for high energy rays lithography and a process for forming a fine resist pattern by using the resist material.
A photoresist delineable with visible rays or near ultraviolet has hitherto been employed as a pattern-forming material in the fields such as masking and production of semiconductor elements, and such a resist has been sufficient to obtain openings on the order of several micronmeters. In recent years, however, finer and finer patterns are desired with demands for decreasing the weight and increasing the capacity of electronic parts, and therefore it is necessary to obtain openings of less than several micronmeters, particularly less than 1 .mu.m.
The conventional photoresist material utilizing longer wave length rays such as visible rays is not applicable to the formation of a fine pattern of several .mu.m. to 1 .mu.m. or less, and consequently a resist material utilizing high energy rays such as far ultraviolet rays, X-rays and electron beams has been developed for enabling the formation of a fine pattern. In such resist materials, the most widely employed is polymethyl methacrylate. It has high resolution, but low sensitivity. For instance, the sensitivity to L-line of Mo which is soft X-rays is 1,300 mJ/cm..sup.2, and the sensitivity to electron beam is 1.times.10.sup.-4 coulomb/cm..sup.2. Therefore, it takes a long period of time to form a pattern.
Also, it is proposed in U.S. Pat. No. 4,125,672 to employ homopolymers of fluoroalkyl methacrylates as resist materials for high energy rays. This resist material is improved in sensitivity which is the defect of polymethyl methacrylate, but often shows poor adhesion property to a certain kind of substrate such as silicon substrate which results in lowering accuracy. For instance, upon development, peeling off or blister of the resist film occurs, due to soaking of a developer into the interface between the resist film and the substrate, and as a result, the concaved portion formed in the substrate by etching, etc. has a larger size than predetermined size. In some cases, such a drawback is eliminated by post-baking, but in most cases, it can be eliminated unsufficiently.
It is an object of the present invention to provide a resist material of positive type having high sensitivity, high resolution and excellent adhesion property.
A further object of the invention is to provide a resist material capable of forming a fine pattern.
Another object of the invention is to provide a process for forming a fine resist pattern.
These and other objects of the present invention will become apparent from the description hereinafter.